1. Field of the Invention
The present invention relates to a both-face automatic original feeding apparatus, and more particularly, it relates to an automatic original feeding apparatus which is incorporated into an image forming apparatus such as a copying machine, a laser beam printer and the like and in which a plurality of originals having images on their both surfaces are automatically and successively conveyed to a reading position to read the images formed on both surfaces of the originals.
2. Related Background Art
In automatic original feeding apparatuses incorporated into an image forming apparatus such as a copying machine, a plurality of originals are automatically and successively sent to a reading position to read images formed on the originals and the read originals are successively discharged. In this case, when the images to be read are formed on front and back surfaces (i.e. first and second surfaces) of the original, the original is reversely rotated (i.e. turned up) so that the image formed on the first surface and the image formed on the second surface can be automatically read.
The original having the images on its both surfaces is firstly supplied from an original stacking portion to a predetermined position, i.e. a reading position for reading the original, thereby reading the image formed on the first surface of the original. In case of an original having an image on its first surface alone, after the image formed on the first surface is read, the original is then discharged from the reading position. On the other hand, when the original also has the image on its second surface, after the image formed on the first surface is read, the original is temporarily stored in a switch-back path, for example. Then, the original is supplied to the reading position again through a path (reverse rotation path or surface reverse path) different to a path through which the original was sent to the switch-back path, thereby reading the image formed on the second surface. After the image formed on the second surface is read, the original is discharged from the reading position. By repeating the above-mentioned series of operations (i.e. the operation for supplying the original to the reading position to read the image on the first surface, the operation for temporarily storing the original in the switch-back path after the reading of the first surface image, the operation for supplying the original to the reading position again to read the image on the second surface, and the operation for discharging the original after the reading of the second surface image) for each original, the images formed on both surfaces of the plural originals can be automatically turned up and automatically read without manual operation.
Incidentally, in the image forming apparatus, an electrostatic latent image corresponding to the read image is formed on an image bearing member such as a photosensitive drum, and then the latent image is developed as a toner image which is in turn transferred onto a transfer material such as a paper sheet. Thereafter, the toner image(s) is fixed to the transfer material and then the transfer material is discharged from the image forming apparatus as a finished copy.
According to the above-mentioned conventional technique, after the reading of the image formed on the first surface of the original is finished and before the reading of the image formed on the second surface of the same original is started, there must be provided the reverse rotation time for turning up the original, which does not directly contribute to the actual image reading. By the way, in the case where the both-face imaged originals are continuously copied, even when the above-mentioned reverse rotation time is provided for each original in addition to the image reading times, if a copying speed of the image forming apparatus is not so high, the reading of the images on both surfaces of the original and the reverse rotation of the original can be effected within the total copying time determined by the copying ability of the image forming apparatus, and, thus, the substantial copying time is not increased.
However, in recent digital copying machines in which digital reading and memory storage are combined, the copying operation is effected at a very high speed to reduce the copying time, so that it is difficult to effect the reading of the images on both surfaces of the original and the reverse rotation of the original within the copying time. That is to say, in case of one-face original having the image on its one surface alone, since there is no need to provide the reverse rotation time, the originals can be successively read continuously to minimize the reading time. However, in case of the both-face original having the images on its both surfaces, since the reverse rotation time must be provided as well as the reading time, the reverse rotation time causes a bad influence, such as lost time.